Abstract
The pathophysiological background of involuntary movements in pseudochoreoathetosis is unclear. We therefore recorded in four patients with pseudochoreoathetosis and in six ageβmatched controls cortical activity with a wholeβhead magnetoencephalography (MEG) system and surface EMGs from hand muscles. Subjects performed the following tasks: 1) rest, and 2) constant finger stretch during forearm elevation; controls additionally simulated pseudochoreoathetotic finger movements. During rest, the patients showed involuntary finger movements associated with excessive MEGβEMG coherence at frequencies between 6 and 20 Hz, whereas coherence in controls simulating pseudochoreoathetotic movements did not exceed noise level (P < 0.02). During finger stretch, MEGβEMG coherence in patients was similar to that of controls. Cortical sources of MEGβEMG coherence in patients were localized in the contralateral motor cortex. We conclude that pseudochoreoathetosis is associated with pathologically increased corticomuscular coherence and thus differs, neurophysiologically, from voluntarily simulated pseudochoreoathetotic movements. The enhanced MEGβEMG coherence in pseudochoreoathetosis probably reflects a pathologically strong motor cortical drive of spinal motorneurons after deafferentation. Β© 2001 Movement Disorder Society.